1. Field of the Invention
This invention relates to a monoclonal antibody, a method for the measurement of a glucosylated protein by using the monoclonal antibody, said method being useful for the diagnosis of diabetes, and a kit for the measurement, as well as a glucitol-lysine derivative useful in the practice of the measuring method.
2. Description of the Prior Art
In recent years, non-enzymatic sugar-protein binding reactions are found to take place in organisms, especially, in those of diabetics. Such non-enzymatic binding reactions are those between aldehyde groups of glucose contained at a high concentration in blood and N-terminal and side-chain amino groups of proteins having relatively long half-life periods and contained in organisms. It has also been elucidated that aldimine (Schiff's base) bonds, which are formed by the above binding reactions, are converted into stable keto-amine bonds through the Amadori rearrangement, thereby forming glucosylated proteins. It has also been revealed that the measurement data of these glucosylated proteins are closely correlated with blood sugar levels during fasting and moreover, the data of diabetic subjects are high enough to distinguish them clearly from the corresponding data of non-diabetics. Accordingly, such glucosylated proteins are effective as indices for controlling blood sugar levels. Their measurement data are useful for the diagnosis of diabetes, the assessment of pathemas, prognostication, and the like. The measurement of glucosylated proteins has therefore great clinical significance.
As methods for the measurement of the above-mentioned glucosylated proteins, there has conventionally been known the TBA (Thiobarbituric acid) method, namely, to add a mild acid to serum and then to heat the resultant mixture to release 5-hydroxymethylfurfural (5-HMF), followed by colorimetric measurement of a color produced through the binding of 5-HMF with thiobarbituric acid (TBA); or the method using boric acid affinity chromatography, namely, to subject aminophenylboric acid to a gel column which has been prepared by immobilizing aminophenylboric acid on a suitable carrier such as "Sepharose CL-6B" (trade name) or the like to adsorb glucosylated protein by making use of protein-bound cis-diol groups of sugar, to elute and separate glucosylated proteins adsorbed on the gel, and then to subject the thus-separated glucosylated proteins to colorimetry by ultraviolet absorption or the Lawry's method.
With a view toward facilitating the operation and enabling fast measurements, it has also been studied to measure the above-mentioned glucosylated proteins by immunoassay. Some antiserum have already been proposed for such applications.
However, the conventional measuring techniques were still unable to meet the needs of the present field of art, especially, in view of accuracy and reproducibility in addition to operational problems such that the operation was complicated and long time was required for measurements [see, "Rinsho Kensa" MOOK, No. 18, pp 60-68 (1984) and Japanese Patent Laid-Open No. 119264/1984].
Under the above-described circumstances, there has been a strong demand in the present field of art for the development of a new measuring technique which can replace conventional methods for the measurement of glucosylated proteins, has still higher specificity enabling appropriate detection of non-enzymatic glucosylation in people to be tested, is hence excellent in accuracy and reproducibility, permits simple and fast measurements, and is also suitable as a screening method.